We are currently pursuing the hypothesis that the major molecular target of NSAIDs is the Heat shock protein, Hsp90. However, it may also involve Hsp70/Hsc70 as well. To address this idea we are using a new CTEP agent that inactivates Hsp90 (Geldanamycin and 17-AGG) in collaboration with Drs. Len Neckers and Elisa Kohn. Results in the laboratory demonstrate that both agents are very significant radiosensitizers and less potent hypoxic radiosensitizers. In addition, they are also cytostatic and induce a inhibition of tumor cell proliferation from a G2/M cell cycle arrest. Initial biochemical data suggests that several cytoprotective and cell cycle signaling pathway regulatory proteins, including Erk, Akt, Raf, Cdc25C, cyclin B1, and Cdc2, are degraded following exposure. The laboratory is pursuing two paths in the area, basic science and translational. The basic science project involves the idea that Hsp may play a role in the regulation of cell cycle progression. Our hypothesis is that Hsp 90 plays a role in the regulation of subcellular localization of regulatory proteins controlling the G2/M cell cycle checkpoint. We are also validating the radiosensitizing effects of 17-AAG in vivo and adding functional kinase proteomics to the in vitro observations of decreased protein levels of factors regulating cytoprotective-signaling pathways.